1. Field of the Invention
The present invention relates to a method and device for controlling a beginning point of an optical pick-up unit, and more particularly to a method and device for moving the optical pick-up unit to a beginning point of an optical disc such as a DVD (Digital Versatile Disc) in order to execute a servo-tuning function.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional optical disc driver such as a DVD player. Referring to FIG. 1, the conventional DVD player includes an optical pick-up unit 20 for reading/writing data from/to an optical disc 10 such as a DVD, a spindle motor 21 for rotating the disc 10, a sled motor 22 for moving the optical pick-up unit 20 to an inner or outer portion of the disc 10, a limit switch 23 for generating a low signal L when the optical pick-up unit 20 moves to the innermost data track of the disc 10, a RF unit 30 for filtering an output signal of the optical pick-up unit 20 to create a binary signal, and a DSP (Digital Signal Processor) 40 for restoring the binary signal to original data according to its own clock being phase-locked with the binary signal.
The conventional DVD player further includes an MPEG decoder 50 for decoding the restored data generated from the DSP 40 according to an MPEG scheme, a motor drive 60 for applying a proper drive voltage to the spindle motor 21 and the sled motor 22, rotating the disc 10 and sliding the optical pick-up unit 20, and a microcomputer 70 for determining a current position of the optical pick-up unit 20 based on an output signal from the limit switch 23, and performing a servo-tuning operation.
Typically, if the disc 10 is inserted into the DVD player shown in FIG. 1, the microcomputer 70 executes a servo-tuning function to read the disc 10. In this case, the microcomputer 70 controls the optical pick-up unit 20 to be located at an innermost data track (also called a beginning point) of the disc 10, and then executes a servo-tuning operation. However, since the microcomputer 70 is unable to recognize a current position of the optical pick-up unit 20 before reading the disc 10, it firstly moves the optical pick-up unit 20 to the beginning point (i.e., the innermost data track) of the disc 10 prior to executing the servo-tuning operation. This operation will hereinafter be described in more detail.
If the disc 10 is inserted into the DVD player, the microcomputer 70 applies a proper drive voltage to the sled motor 22, and moves the optical pick-up unit 20 to the beginning point (i.e., innermost data track) of the disc 10. In this case, the limit switch 23 outputs the signal L when the optical pick-up unit 20 is placed at the innermost data track of the disc 10, such that the microcomputer 70 continuously checks the output signal of the limit switch 23 while the optical pick-up unit 20 is in motion in order to determine whether the optical pick-up unit 20 has been moved to the innermost data track.
When the optical pick-up unit 20 finally moves to the innermost data track, the microcomputer 70 executes a prescribed servo-tuning operation.
However, the aforementioned conventional DVD player must adapt an additional limit switch to determine whether the optical pick-up unit 20 has been moved to the innermost data track of the disc 10, resulting in the increase of size and cost of the DVD player.